Bulletin of the Chemical Society of Japan
Online ISSN : 1348-0634
Print ISSN : 0009-2673
ISSN-L : 0009-2673
Iodine-catalyzed Thermal cis-trans Isomerization of Azobenzene
Shigeru Yamashita
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1961 Volume 34 Issue 6 Pages 842-845


The equilibrium of 1 : 1 molecular complex formation between cis-azobenzene and iodine in n-hexane has been studied spectrophotometrically in the temperature range 10∼25°C. The heat of formation of the complex has been found to be −ΔH=7.5 kcal./mol. The rate of iodine-catalyzed isomerization of cis-azobenzene determined spectrophotometrically in n-hexane solution has been found to be proportional to the concentration of cis-azobenzene as well as to that of iodine, with an activation energy of 6.3 kcal./mol. over the temperature range 30∼50°C. The most probable interpretation of the rate measurements is that the complex of cis-azobenzene with iodine isomerizes with an activation energy of 13.8 kcal./mol. under the experimental conditions of the present work.

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